Jing Pan

Mon, Jun 23, 2025, 4:43 AM6 min read

Moneywise and Yahoo Finance LLC may earn commission or revenue through links in the content below.

Kevin O’Leary has made numerous investment bets on Shark Tank, backing everything from kitchen gadgets to cat DNA testing. But when it comes to teaching his own kids about money, his advice is surprisingly simple.

“What piece of advice do I give my kids over and over and over again about money? Don’t spend it, save it, invest it, let it compound — that’s the gift the market gives you,” O’Leary said in a recent YouTube video.

“Take 15% of all your paychecks, all your side hustle, any cash granny gives you, and put it in the market and just let it compound.”

Saving 15% might not sound like a fast track to riches, but O’Leary says the payoff can be enormous — even on a modest income.

“If you make $68,000 a year, the average salary, and you do this your entire life — just 15% of your paycheck — you’ll end up a millionaire at retirement at 65.”

It’s a compelling idea. But how realistic is it?

• Thanks to Jeff Bezos, you can now become a landlord for as little as $100 — and no, you don't have to deal with tenants or fix freezers. Here's how

• BlackRock CEO Larry Fink has an important message for the next wave of American retirees — here's how he says you can best weather the US retirement crisis

• Nervous about the stock market in 2025? Find out how you can access this $1B private real estate fund (with as little as $10)

The outcome depends on key factors like when you start and what kind of return the market delivers. For example, CNBC estimates that if you begin saving 15% of your income at age 25 and earn a 4% annual return, you’d only need to make $67,459 a year to hit the $1 million mark by 65.

Start at 40, however, and you’ll need to earn more than double — $155,086 per year — to reach the same goal with a 4% return. But if you manage to get an 8% return, the required income drops to $83,563.

Historically, the U.S. stock market has delivered strong long-term returns. The benchmark S&P 500’s average annual return has hovered around 10%, though of course, past performance is no guarantee of future results.

Still, O’Leary’s core message is timeless: the earlier and more consistently you invest, the better your chances of growth.

“Best piece of advice I can give anybody,” he said. “Don’t buy stuff you don’t need — invest it instead.”

Here’s a look at a few simple ways to apply that advice in your own life.

O’Leary’s advice to “put it in the market and just let it compound” echoes the philosophy of investing legend Warren Buffett.